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Energy Insurance for Anchorage, Alaska--Beluga River Gas Field, Cook Inlet

Norman D. Stone, Robert G. Lindblom

The Beluga River gas field is the primary energy source for Anchorage, Alaska. The field is located 40 mi west of Anchorage astride the northwest shoreline of the Cook Inlet. Gas was discovered in December 1962 by Chevron's Beluga River unit (BRU) 1 well in section 35, T13N, R10W, S.B. and M. There are 16 producing wells in the field capable of a total gas potential of 140,000 MCFD. The current production averages 75,000 MCFD and the field has produced 220 BCF gas. Chevron, Shell, and ARCO have equal interests in the field. The Beluga River unit was formed in 1962 with Chevron as operator. The produced gas is sold to the Chugach Electric Company and the Enstar Gas Company, both Anchorage-based utilities.

The gas accumulation is trapped by a doubly plunging, slightly asymmetric anticlinal fold trending northeast-southwest. Gas is found from 3,000 to 6,000 ft vertical depth in sands within the lower Sterling (Pliocene) and Beluga River (upper Miocene) Formations. Reservoir sands range in thickness from 5 to 85 ft with average porosities of 24 to 30%. The Sterling sands were deposited in broad sand channels in a fluvial-deltaic setting, whereas Beluga sands were deposited in a high-energy fluvial environment in shifting stream courses.

The use of the wireline repeat formation tester has aided in correlation, evaluation, and management of the multiple sand reservoirs. New gas sand reservoirs and partly depleted reservoirs are recognized, enabling completion from reservoirs of similar pressures and reducing risks associated with cross flow between reservoirs.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.